Electronic warfare involves a generation of high-power RF pulses which are incident on target radars/receivers so as to either result in jamming or to in fact cause massive malfunctions of the receiving apparatus. It has been the goal of those involved in electronic warfare to be able to put a considerable amount of energy on a target and to tailor the energy both in frequency and in pulse repetition rate to match that of the target's vulnerabilities. Target radars are now considerably more sophisticated and operate on the basis of coded signatures so as to be able to defeat jamming systems by being able to filter out indiscriminate jamming that doesn't take into account the sophistication of the target radar. Also, in communication systems, it is often times required to be able to disable these systems by the infusion of RF energy that causes these systems to malfunction.
In order to confuse or disable target receivers or electronics, be they microwave radars, or other types of communication systems, it is common to provide high power RF pulses generated by photoconductive switch-based RF generators. The present switch-based RF generators utilize silicon-based switches which are activated by pulsed lasers, the laser pulses of which serve to close the switches. The closing of the switch in general grounds a transmission line that has been charged from a high-voltage source, with the grounding of the transmission line causing a negative going RF pulse to be generated.
Thus, generation of high power pulsed RF waveforms has in the past been accomplished through the momentary grounding of a transmission line which is coupled to a high-voltage source, in which the grounding of the cable produces a negative going voltage spike that creates an RF waveform which propagates out through an antenna.
As mentioned above, this momentary grounding has been provided through silicon switch technology. The problem with such silicon technology is primarily the long carrier lifetime which limits the repetition rate and thus the frequency of the RF output as well as the ability to specifically tailor the outgoing RF waveform. Moreover, silicon technology has a limited voltage holding capability that limits output power and also offers only a limited tuning capability. Thus, photoconductive switch-based RF waveform generators based on silicon are limited to frequencies in the kilohertz pulse repetition rate range and are further restricted by the limits on the high-voltage supply.
Additionally, the silicon-based photoconductive switch RF generators are not capable of putting enough energy on a target unit, either because the RF output pulses are not powerful enough or because these systems cannot rapidly fire RF pulses on target. With silicon technology the building up of pulses to be fired in rapid succession on a target is simply not possible. For instance, it is not possible, utilizing silicon switches, to generate multiple high-power pulses in a single, rapid burst.
It will be appreciated that a single laser pulse applied to a silicon switch closes the switch for tens to hundreds of microseconds due to the long carrier lifetime associated with silicon, with the switch closure completely discharging a transmission line due to the long switch closure. Since there is no further charge in the transmission line this precludes multiple high-power RF pulses generated during the time it takes the silicon switch to recover. The result is that when one uses silicon switch technology only a single high-powered RF pulse can be generated once every 10 to 100 μs.
Further, due to the fact that only a single output pulse can be generated with silicon switching systems every 10 to 100 μs, there is no possibility to provide additional laser shots within this 10 to 100 μs silicon switch recovery time, i.e. prior to the completion of the initial transmission line discharge phase.